Environmentally beneficial bypass filter system for use with low pressure centrifugal refrigeration equipment

ABSTRACT

A bypass filter system for use in low pressure, centrifugal type refrigeration equipment which allows complete isolation of a submicron filter element from the lubrication system through use of an inlet line shut-off and a return line shut-off. The filter system utilizes a variable regulator valve for balancing the operating parameters of the various systems involved to permit initial installation and set up, at which point thereafter the variable regulator may be replaced with a fixed regulator for continued operation of the system. Multiple devices for monitoring the filter element condition, verifying flow, detecting moisture, and displaying pressure readings may be used in conjunction with the basic device to enhance reliability and usefulness. The invention may further be enhanced by the utilization of valves which allow samplings of the unfiltered and filtered oil, such samplings being subjected to tests to verify the improved quality of the filtered oil, indicating proper operation of the system, or to verify a system degradation by showing an unimproved filtered sampling.

FIELD OF THE INVENTION

This invention relates to bypass filter systems for lubricating oil, andparticularly bypass filter systems used in refrigeration equipment. Morespecifically, the invention relates to bypass filter systems used in lowpressure, centrifugal type refrigeration equipment.

BACKGROUND OF THE INVENTION

Like almost all machinery with moving parts grinding together,refrigeration equipment needs proper lubrication to operate. Goodlubrication with clean oil can maintain a refrigeration compressor inservice for extended periods with little other maintenance. A poor oilquality can cause continual problems, some of which may go unnoticeduntil the equipment has a catastrophic breakdown.

Unlike other machinery, such as a car engine, however, the oil in arefrigeration system cannot practically be changed every two months toassure a clean system. The reason is related to ozone depletion. Eachtime refrigeration equipment is opened or purged there is some releaseof refrigerant, usually CFC, to the atmosphere. This has been linked tothe alarming decimation of the earth's ozone layer--the once thickblanket of O₃ which helps to filter out harmful components of the sun'srays. Thus lubrication maintenance for refrigeration systems has evolvedto its own unique process.

Historically, the oil used to lubricate and cool the moving parts inrefrigeration equipment, such as chillers, has been drained and replacedannually. The service branch of the equipment manufacturer would haulaway and dispose of the used oil as would other outside service vendors.More recently, individuals and companies have frequently paid a fee as abuilt-in cost in a service contract to have their waste oil hauled away.Some of the oil was reclaimed, after which it could then be resold,usually as a lower grade oil.

However, changes are rapidly taking place in the industry. It isbecoming increasingly difficult as well as costly to arrange fordisposal of the oil. Great concerns have been raised by variousgovernment agencies regarding such oil as a hazardous waste. Morealarming is the anxiety created by the release of harmful refrigerantsinto the atmosphere each time the seal is broken on these refrigerationdevices. Most notably is the low pressure centrifugal type equipmentwhich uses R-11 refrigerant. Those still using the machinery continuallyface fines for the release of R-11 above a certain mandated amount. Itis believed that literally hundreds of thousands of these offendersexist.

The present invention has sought to address these problems in the lowpressure centrifugal type refrigeration equipment. And in fact, thepresent invention has sought to anticipate further restrictions andproblems linked to pending legislation which may reduce the limits forrelease of R-11 into the atmosphere.

In understanding the nature of the problem addressed, it is essentialthat a distinction be made between the low pressure class of equipmentand their heavily legislated high pressure counterparts. Because the lowpressure class of systems have presented far less safety risks in theindustry they have been almost unrestricted in their use. On the otherhand, equipment classified as high pressure has evolved under continuousrestriction. The high pressure class of equipment is forced to meetcountless ASHRAE/ASME/ANSI/ASTM codes. This of course increases the costof the refrigeration equipment dramatically. High pressure centrifugalequipment requires more KW per ton of cooling than its counterpart (lowpressure), and is dramatically more dangerous to operate. Maintenancecosts are higher for the high pressure vessels, and the operating staffmust be more specialized than those operating the low pressure machines.Perhaps a key difference is that the high pressure machine has no vacuumon the low side line and is generally tested at between 300 pounds persquare inch (psi) to 600 psi. The result of thisgreater-than-atmospheric pressure internally is that air does not leakinto the equipment during operation. Atmospheric leaks intorefrigeration equipment are instrumental to mechanical degradation, andparticularly harmful to the lubricating oil. When high pressure machinesare tight and properly evacuated at start-up or after service, internalmoisture does not become a factor in their operation. For this reason,high pressure machines do not have, or need, an automatic purge cycle tokeep air out of the system.

Conversely, low pressure equipment, the focus of the present invention,has been much less regulated. Presently it does not have to meet theregulations set forth by the higher pressure vessels. These machines aregenerally tested at 30 psi and operate under 15 psi. They may reach 15"(Hg) of vacuum on the low (suction) line side, and even lower duringevacuation of the filter housing. Typically, the low pressure machine isabout 35% larger than high pressure centrifugal equipment. Depending oninternal and external conditions, while the machine is in its idleoff-state, the equipment will assume a negative pressure internally.This negative pressure state constantly has the potential of allowingair to leak into the system. Each leak is the possible propagator ofcatastrophic failure. As the temperature falls inside the machine thewater vapor within the atmosphere condenses into droplets on the metalsurfaces. The water in turn reacts with other contaminants to produceacids that may break down motor windings and erode metal surfaces. Tohelp counter-act this problem, those skilled in the art have utilized apurge pump. The pump automatically starts when air or water is presentin the purge system and stops when the air and/or water has beenremoved. Not only does this pump push the air out of the machine, but asignificant amount of the refrigerant leaves as well. The process of thepresent invention traps the water, thus reducing the amount of run timeof the purge pump and thus reducing the amount of R-11 pumped into theatmosphere.

These distinct differences between high and low pressure refrigerationequipment have led those skilled in the separate arts to address verydifferent problems. To these persons skilled in the representative arts,what generally applies to one, such as internal equipment leaks in lowpressure, does not necessarily apply to the other. Furthermore, whilethe use of the purge pump system addresses the problem of watercontamination in a low pressure system, it does so at the cost of moreimportant environmental concerns.

Ancillary to the high vs. low pressure classification is the distinctionbetween refrigeration equipment types. In the field there existscentrifugal type equipment, as shown in U.S. Pat. Nos. 4,404,812 toZinsmeyer, 4,032,312 to Anderson, 3,650,634 to Osborne et al., and3,163,999 to Ditzler et al., and piston and screw type equipment, asshown in U.S. Pat. No. 4,586,875 to Aman, Jr. (piston type compressor).The latter two types are strictly high pressure class equipment withvery different lubrication and operational concerns, while centrifugaltype equipment can be either low pressure or high pressure. The presentinvention focuses on the low pressure centrifugal type equipment.

Some of the major problems inherent to low pressure, centrifugal typerefrigeration equipment are water caused by condensation, and water dueto leaks in the oil cooler system. As this water mixes within the systemit forms hydrochloric acid (HCl), an extremely caustic acid. The acidtends to degrade the system by destroying internal parts. Severaldevices, such as that disclosed in U.S. Pat. Nos. 4,975,188 to Brunsellet al., 4,830,745 to van der Meulen, 4,687,572, 4,591,433, and 4,534,860all to Budzich, teach the removal of water from lubricating oil, but theoil must first be removed from the lubricating system. These particulardevices are called centrifugal type separators, not to be confused withcentrifugal type refrigeration equipment. The separators subject theoil/water mixture to high velocity centrifuging to obtain separation ofthe various liquids. The water is then drawn off to leave just the oil.Separators of this type are not well suited for use in refrigerationequipment because of their size--they are typically suited for largevolume separation--and cost.

In U.S. Pat. Nos. 3,208,596 to Gravert and 4,892,667 to Parker III, etal., water removal is taught in lubricating oil systems using coalescingfilters. This procedure consolidates tiny water droplets into largerwater droplets which, when they reach a certain size, may be removed bygravity. Gravert uses hydrophobic screen separators (10 microns averageopening size) to block the passage of any water droplets, while stillallowing the passage of oil. The very size of the coalescing apparatusdoes not make it a practical solution to the water problem in lowpressure centrifugal refrigeration equipment.

Somewhat related to the problem of water contaminants is that of minuteor submicron particles. As these tiny contaminants build up in any typeof machinery they can cause great wear and tear on the moving parts. Infull flow filtering systems, submicron filtering is not achievablebecause of the necessary retention needed to be effective. Longerretention of the oil in these full flow systems would naturally causethe lubrication system to be starved of oil, or perhaps require animpractical amount of surplus oil to operate. Thus, bypass filters havebeen used to provide submicron filtering for smaller portions of the oilsupply. After several passes through the bypass system as much as 98% ofthese submicron particles can be removed. However, in low pressurecentrifugal refrigeration equipment one is presented with the problem ofsufficient filtering due to a positive pressure inlet side and anegative pressure on the low (suction) side. Under these circumstancesthe oil has a tendency to exit the filtering unit without beingadequately retained for effective filtration. Those havingrepresentative skill in the art have not recognized the benefits ofbalancing the operating parameters of the filtering system tosufficiently filter oil at a submicron level without starving thelubrication system. Attempts have been made to control the inlet portionof oil, but efforts have fallen short of metering the return of filteredoil. This is particularly true for newly established equipment which hasno guidelines to follow for setting these parameters correctly. Thepresent invention is designed to allow careful balancing of theessential operating parameters to provide a reliable oil filteringsystem on both existing and new systems.

One of the most difficult situations faced by those using the lowpressure centrifugal refrigeration equipment is the need to shut downthe equipment for routine filter and oil changes. The process caninvolve several hours of discontinued operation of the equipment. Due tothe considerable cost involved there is little redundancy in the fieldof cooling apparatus (i.e., use of backup systems). Shutting a coolingsystem down for even a short period of time can cause a considerableamount of inconvenience. Yet all known devices require discontinuedoperation of the refrigeration system to carry out a routine maintenanceprocedure such as changing the oil filter. Perhaps surprisingly, thoseskilled in the art did not realize that it would be possible to isolatethe filtering system entirely, thereby permitting continued operation ofthe lubricating system and therefore continued operation of therefrigeration equipment during routine oil and filter changes. Certainlybypass filter systems have been known for some time. However, one whichallowed the filter to be changed without discontinuing operation of theequipment had not, until the present invention, been available inrefrigeration systems.

Environmentally, the main concern however, with shutting down themachine is more the release of CFC's into the atmosphere. As alluded toearlier, there are numerous government agencies which have sought toimpose stiff penalties on R-11 users. With the annual release of R-11into the atmosphere by approximately 500,000 low pressure centrifugaltype refrigeration systems, the environmental impact becomes quitealarming. Such dangers of refrigerant release into the atmosphere arewell documented in U.S. Pat. Nos. 4,805,416 to Manz et al., 4,261,178 toCain, 4,110,998 to Owen, 3,699,781 to Taylor, 3,145,544 to Weller, and2,341,429 to Elsey. The present invention would require less frequentmaintenance to replace degraded lubrication oil. It is anticipated thatoil changes could be performed every five years, rather than thestandard one year. These changes could be coincided with thespecification check-ups which are performed every five years as well.Theoretically the reduction of R-11 released into the atmosphere eachyear would be 80%. The key to this practice would be to maintain the oilin a suitable lubricating state, without degradation due tocontaminants.

The present invention, in both its apparatus and methods, recognizes andaddresses these problems and overcomes the limitations perceived bythose skilled in the art by presenting a design which, among otheraspects, allows for the removal of water, glycol and submicron particleswithout having to shut down the refrigeration system. Those skilled inthe art of low pressure centrifugal refrigeration equipment design havelong been aware of these problems of water degradation of oil, submicronparticle impurities, and environmental contamination. Millions ofdollars have been spent to date in both research and fines by thoseusing low pressure centrifugal equipment. All the while the necessaryarts and elements for implementing the disclosed invention have existedfor sometime. The various patents cited show substantial attempts bythose skilled in other fields to solve each of the above problemsseparately as they exist in their particular art. That is, some havebeen able to remove submicron particles from lubricating oils, othershave accomplished water removal by oil reclamation or by use of thestandard purge pump, and still others have addressed the environmentalconcerns. However, a system which integrates these capabilities into thepermanent filtering system of low pressure centrifugal typerefrigeration equipment has not existed until the present invention.Instead of understanding the true problem, manufacturers have coped withthe inherent limitation to some of these devices and methods, such asthe purge pump. There appeared to be a failure to fully understand theproblems and impacts of properly filtering lubricating oil in lowpressure centrifugal type refrigeration equipment.

SUMMARY OF THE INVENTION

The present invention discloses a bypass filtering system to operate inconjunction with low pressure centrifugal type refrigeration equipment.The device provides a reliable and efficient method for filteringlubricating oil. Rather than supplying a system which affords only anincremental increase in performance and design over the prior art, thepresent invention utilizes techniques which were not previouslyconsidered to achieve leaps in performance compared to the prior art.This invention serves to optimize cost efficiencies for the user byrequiring less frequent maintenance, to optimize the reliability of therefrigeration system, and to optimize solutions to environmentalconcerns.

In general terms, the invention involves embodiments of both methods andapparatus. Many of the elements of this system achieve several differentobjects which, when combined, act to achieve the mentioned leaps inperformance. In one embodiment, the invention discloses shut-off valvesfor isolating the bypass filter system from the lubricating system,allowing continued operation of the refrigeration equipment duringroutine filter changes. In another embodiment, the filtering system iscapable of removing harmful water and glycol contaminants. In stillother embodiments, the present system discloses the use of pressuregauges and moisture eyes to verify operation and monitor filter elementconditions.

Importantly, the invention breaks from several time-honored traditionsin filtering lubrication oil in a refrigeration system. While drawingfrom some of the important conditions demanded of these devices forproviding an effective filter system, the invention expands upon theseconditions in an effort to provide an efficient and reliable device.With submicron particle removal by the filtering element, oildegradation can be impeded to minimize maintenance requirements andthereby reduce environmental harm. By recognizing and utilizing theadvantages of complete isolation of the filter system the presentinvention achieves its goals.

Accordingly, the present invention provides a bypass filter systemmethod and device which isolates the filter element from the lubricationsystem. The stated device provides means for monitoring and detectingineffective filter elements and water leaks, whereby the filter elementmay be isolated and replaced without disruption of the continuedoperation of the refrigeration system. The present device may includeflow regulators for properly balancing the operation parameters of thevarious systems involved. In addition, the device utilizes submicronfilter elements in a manner to further facilitate impedance of oildegradation.

One object of the present invention is to provide a design which avoidsstarving the lubricating system of oil, while providing properfiltration of the oil. It is therefore an object to provide a means forbalancing the operating parameters of the various systems involved onboth existing and new refrigeration equipment. These means may besupplied by monitoring and controlling the return flow rate in thefilter element, or they may also be accomplished by maintaining suitableretention of the oil in the filter element.

It is also an object of the present invention to provide a design whichallows isolation of the filter element by means of both an input andreturn flow shut-off valve. As a benefit the present invention iscapable of allowing the refrigeration equipment continued operationduring routine filter changes.

It is another object of one embodiment of the present invention toprovide a design which removes harmful contaminants at all levels. Thatis, a system which can remove large particle contaminants, as well assubmicron contaminants, as well as liquid contaminants, such as water orglycol. It is an object to enable the present invention to extend theusable life of the machinery as well as the oil by such filtration.

Another object of the present invention is to provide a design whichmonitors the physical state of the submicron filter element. By such,the present invention is capable of such an object as detecting waterleaks in ancillary systems, such as the oil cooler system coil. Gaugeswhich monitor the pressure within the filter element housing react tofilter degradation, due to particle build up or increased waterabsorption, by displaying the resultant higher pressure readings. It isan object that such a system serve as an early warning to operators ofsuboptimal conditions.

Naturally, other objects of the present invention are disclosedthroughout various areas of the specification and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The following descriptions and referenced drawings are for selectedpreferred embodiments of the present invention. Naturally, changes maybe made to the disclosed embodiments while still falling within thescope and spirit of the present invention and the patent granted to itsinventors.

FIG. 1 is a block diagram showing the basic elements of the presentinvention and their relationship to one another. The arrows illustratethe direction of travel of the oil in the entire system.

FIG. 2 is a detailed side view of the bypass filter system as it wouldbe attached to the oil pump in low pressure centrifugal typerefrigeration equipment.

FIG. 3 is a side view of the bypass filter system. The arrows illustratethe direction of oil through the system.

FIG. 4 is a cross-sectional view of the filter element housing. Thearrows illustrate the direction of oil through the filter element.

FIG. 5 is a close-up view of the attachment of "T" to the oil supplypressure gauge line.

FIG. 6 is a close-up view showing diagrammatically the attachment of aclosed nipple to the oil pump to displace the existing oil drain valve,which is relocated to an opening on the adjoining "T", also shown.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

As can be seen from the drawings, the basic concepts of the presentinvention may be embodied in a variety of ways. FIG. 1 represents, in ablock diagram form, the basic elements of low pressure centrifugal typerefrigeration system (40), such as oil pump (32), oil reservoir (31),compressor (41) and bypass filter system (10). In general, oil situatedin reservoir (31) is maintained under a vacuum pressure. Oil pump (32)creates the pressure and forces oil through oil supply line (34) and oilreturn line (35). From Oil pump (32) the oil can be circulated to thevarious moving parts of compressor (41). The present invention isintegrated into this system by cutting into oil supply pressure gaugeline (36)--the positive pressure side of pump (32)--with inlet line (13)and displacing existing oil drain valve (38) (as shown in FIG. 2)--onthe negative or suction side of pump (32)--with outlet line (14).

While the designs and concepts disclosed herein focus upon and may finduse for the refining of oil in a bypass filter system of low pressurecentrifugal refrigeration equipment, it may also obviously find use in avery wide variety of other applications. It, therefore should beunderstood that while the field of application of the invention isdiscussed in the limited context, the scope of protection afforded isnot intended to be so limited.

Referring now to FIGS. 2, 3 and 4, the flow of oil through the presentinvention may be more easily understood. The bypass filter system isdivided into three sections, namely the inlet, filter, and outletsections. Beginning first with the inlet section, oil is routed off ofoil supply pressure gauge line (36). This is accomplished by installing"T" (29a) into oil supply pressure gauge line (36), as shown in FIG. 5,by using either a sweat fitting or a flair type union. Of course otherdesigns may be just as suitable and perform as well. From this, inletline shut-off (20) is located allowing the oil supply feeding intofiltering system (10) to be turned off. From shut-off (20) a section ofbraided flex hose or oil conduit (27a) is connected to check valve (15).The braided reinforced hose is preferable to insure high quality, anddurability, but other materials may be used if desired. Check valve (15)is used to prevent backwash of the filtered contaminants back into oilpump (32) when the equipment is turned off or operation discontinued forany reason. This is widely known and used by those skilled in the art.Brass closed nipple (16a) connects check valve (15) to "T" (29b). Oneopening of "T" (29b) is fitted with oil sample valve (22). This permitsa sampling of the unfiltered oil to be taken without disruptingoperation of the lubrication or refrigeration systems. Other advantagesof this sample valve will be addressed later in this text.

By threading closed nipple (16b) into the last opening of "T" (29b) thefilter section is now ready for connection to system (10). Inlet (17) offilter element housing (12) serves as such connection, in thisembodiment. Within housing (12) filter element (11) is situated tofunction as the means for removing all possible sized particles,including those at the submicron level, as well as water and glycolcontaminants. Such filtering elements as those described in U.S. Pat.Nos. 4,780,204 and 4,792,397 to Rasmussen, and manufactured by theHarvard Corporation have been found to be suitable for this process. Thedisclosure of these patents is hereby incorporated by reference. Inaddition, other filter element designs such as that disclosed in U.S.Pat. No. 4,929,354 to Meyering et al., and manufactured by Cuno,Incorporated, may be suitable for certain applications. It might even bepossible to use several filtering and screening devices situated in amanner so that the removal of large and submicron particles areseparately removed, as well as water and glycol contaminants.

Positioned within an opening in lid (19) of housing (12) is closednipple (16c) to allow connection of "T" (29c). The remaining twoopenings of "T" (29c) are fitted with Schrader valve (25) and compoundgauge (26). For added benefit a pressure transducer could be added toreplace or act in conjunction with gauge (26). A transducer would allowwarning devices to be attached to system (10) and activated when theinternal pressure of housing (12) reached a preset value. Compound gauge(26) allows the continuous monitoring of the internal pressure ofhousing (12), which must be kept within certain tolerances as will beexplained later. Furthermore, the use of a compound gauge is preferable(with or without the transducer) since during operation housing (12) isunder an absolute positive pressure, while when turned off the internalpressure may be as low as negative 15" Hg (a vacuum). Gauge (26) mustalso be able to withstand the negative 25" Hg used to evacuate housing(12) after a change of filter element (11). Either of these processeswould of course break, or at the very least upset the calibration of astandard pressure gauge. Schrader valve (25) is used to evacuate housing(12) after changing filter element (11). This process is explained inthe discussion regarding the present invention's operation.

Finally, adjacent to inlet (17) is outlet (18) in housing (12) connectedto closed nipple (16d). At the open end of closed nipple (16d) isattached means for metering oil flow (28). This valve may be a variableflow regulator, such as a needle valve, or a fixed flow regulator, suchas a fixed orifice. While installing the present invention onto existingrefrigeration equipment it is essential that the flow of filtered oilfrom filter element (11) be rigidly regulated. Furthermore, byregulating the flow at the outlet side of filter system (10) greatadvantages are afforded. Regulating the flow of oil makes it possible tobalance the operation parameters of lubrication system (30) to ensureoptimal operation, and filter system (10) to allow sufficientfiltration. It is undesirable to allow the flow through filter (11) tobe too great--this decreases the effectiveness of the water andsubmicron particle removal due to minimal retention of the oil in filter(11)--and it is undesirable to have the return flow too great as thiswill starve the lubricating system of oil, potentially causingcatastrophic failure. A wide practice in the field has been to controlthe flow at the input side of filter system (10). This can only monitorhow fast the oil goes in filter (11), but not how fast it comes out. Bycontrolling the out flow the present invention can control both, andthus balance the necessary operation parameters of the various systems.

The next element is closed nipple (16e) threaded between one end ofmeans for metering (28) and one opening of "T" (29d). To the remainingopenings of "T" (29d) are sample valve (23) and a section of braidedflex hose (27b). This carries the return oil flow to moisture eye (24).The purpose of moisture eye (24) is twofold. First, it serves toindicate the presence of water in the return flow oil. By doing so itmay additionally indicate a problem with filter element (11), such as aclog or saturation. Either case would also cause a significant pressureincrease within housing (12) and should therefore register on compoundgauge (26) as well. In practical use the operator would notice theincreased pressure recorded on gauge (26) and turn to moisture eye (24)for a verification that water exists in the return oil flow. If nomoisture is showing in moisture eye (24) this may indicate a problem incalibration of gauge (26).

The second purpose of moisture eye (24) is to allow verification ofreturn oil flow. Once again, in practical operation if gauge (26) isshowing rapidly increasing pressure, the operator could look to moistureeye (24) which may indicate no current flow, thereby verifying asuboptimal condition, such as a clogged filter element (11).

The flow route continues with return line shut-off valve (21) attachedto the remaining opening on moisture eye (24). Valve (21) is thenattached to one opening of "T" (29e). At this point, as can be seen inFIG. 6, existing drain valve (38) on oil pump (32) is removed andthreaded to one of the remaining openings of "T" (29e), while the finalopening is attached to closed nipple (16f). It is not intended thatdrain valve (38) should be removed entirely, as it may still benecessary to periodically drain the entire supply of oil. In such a casedrain valve (38) is the most practical means for doing so. Closed nipple(16f) fits into the opening created by relocating drain valve (38) onoil pump (32) to complete the installation of the present invention.

The preceding discussion characterizes a single embodiment of thepresent invention. Many of the disclosed elements have suitablereplacement components known by those skilled in the relevant field, andare too numerous to practically enumerate. Where suitable replacementsare known it is intended that these components be included within thescope and spirit of the patent granted on the present invention.

In order to further understand the present invention it is desirable todiscuss bypass filter system (10) as it functions in operation. Thefollowing discussion explains the attachment of bypass filter system(10) to existing equipment. Modifications may be necessary if theequipment is to be manufactured with filter system (10) attached. Thepresent invention, as shown in FIG. 5, is attached to lubrication system(30) at oil supply pressure gauge line (36). Connection at this point isto ensure that no oil is taken from the oil supply line, causingpossible starvation of lubrication system (30). Approximately 10% of thefull flow of oil is routed by this connection to bypass filter system(10). For some older refrigeration equipment it may be desirable toroute as much as 35% of the full flow of oil. Other equipment, forunknown reasons, may require a higher or lower percentage of oil flow.All of these systems may be accommodated by the present invention bydiverting a greater percentage of the full flow to filter system (10).Continuing again with FIGS. 2, 3 and 4, the oil flows toward filterelement housing (12) and it passes through shut-off (20). At this pointthe flow of oil to filter element housing (12) may be completely turnedoff. When utilized with shut-off (21) in return line (14), filterelement housing (12) may be completely isolated from lubrication system(30). This isolation allows an operator to check or replace filterelement (11) without shutting down refrigeration system (40). Currentfiltering designs, and even bypass filtering designs, do not incorporatemeans for isolating the filter element to allow changes, and evacuationof filtering system (10) during continuous operation of therefrigeration system. This alone is a significant advancement in theart.

As with any filter element, that used in the present invention should bereplaced when it degrades to a suboptimal condition. The procedure forreplacing filter element (11) is fairly uncomplicated. Shut-off (20) isclosed off to discontinue flow from filter element (11) and thenshut-off (21) is closed off to complete the isolation. This moreeffectively reduces the CFC's released into the atmosphere. It is thennecessary to drain the oil in housing (12). Inlet sample valve (22) maybe opened to accomplish this step, after housing (12) is opened torelease the pressure. Then filter element housing (12) can be completelyopened to reveal filter element (11). To open housing (12) is veryuncomplicated, for this embodiment. Lid (19) is held in place byaviation band (50) which tightens lid (19) against "O" ring (51) to forma tight seal with filter housing (12). By loosening the t-bolt and nuton aviation band (50) the seal may be broken and lid (19) removed. Afterdraining, the oil filter element (11) may be inspected for defects, orjust replaced outright. Housing (12) is then closed up to conceal filterelement (11). A vacuum pump is connected to housing (12) at Schradervalve (25) and activated to begin evacuating housing (12). This helps toremove any remaining water before continuing operation of filter system(10). When the evacuation is complete--typically housing (12) is takendown to a pressure of negative 25" Hg and held for 1 hour, threetimes--shut-off (20) is re-opened, and then shut-off (21) is alsoopened. The order of opening and closing shut-offs (20, 21) is importantto avoid releasing CFC's into the atmosphere upon opening housing (12)and when filling housing (12) with new oil. The oil needs to flow in thedirection of normal operation. Since no oil is present at check valve(15) the oil may move backwards through filter element (11), releasingentrapped contaminants, if shut-off (21) is opened first.

Schrader valve (25) also may be used to introduce new oil intolubrication system (30). The advantage of adding oil at this point isthat the oil will be filtered before it reaches the moving parts ofrefrigeration system (40). While new oil may be relatively cleancompared to used oil, it still may carry harmful submicron contaminantsand water. By filtering the new oil with the present invention before itenters the lubrication system many of these contaminants can be removedimmediately. Of course oil may still be added in the conventional manneras well.

During operation, before the oil flow reaches filter element housing(12) it passes through check valve (15). This valve is used as a one-waypassage to allow for oil to enter filter housing (12) from inlet line(13), but to prevent a backwash of oil, including a concentration ofcontaminants, from housing (12) through inlet line (13) and into oilpump (32). The oil flow also passes by sample valve (22). Sample valve(22), as mentioned earlier, serves as a means for draining the oil fromhousing (12) before removal of filter element (11), but after isolationof bypass filter system (10). A similar valve, sample valve (23), islocated in outlet line (14). Together the two valves provide a methodfor verifying proper operation of filter system (10). Each valve allowsa sampling of oil to be taken from the respective lines (13) and (14).Sample valve (22) yields unfiltered oil, while valve (23) yieldsfiltered oil. These samples may be tested to confirm that the filteredoil is indeed substantially free of water and contaminants. A comparisonof the samplings would permit calculation of a filtering efficiency bythe following formula: ##EQU1##

The oil flow continues then until it enters filter element housing (12)where it engages filter element (11). The filtering process, of thisembodiment, is described thoroughly in U.S. Pat. Nos. 4,780,204 and4,792,397 both to Rasmussen, and assigned to the Harvard Corporation.These filter elements are currently those used in the present invention,because of their efficiency in removing submicron particles, and water.However, other filtering elements may exist which sufficiently remove atleast some contaminants. It is anticipated that these filters could beused alone or in combination with other filters to accomplish the goalsof the present invention.

The flow of oil at this point, and throughout inlet line (13) is under apositive pressure supplied by oil pump (32). This pressure is about 25lbs, but, of course, may vary widely for other applications. At meteringdevice (28) the pressure changes to a negative pressure. Also widelyvariable, but in the present embodiment it is about negative 15" Hg. Thenegative pressure is generated by the refrigerant itself as it undergoesa temperature change, and by the operation of compressor (41), as well.The absolute pressure of housing (12) is registered by compound gauge(26). This particular pressure set-up would normally cause a rapid exitof the oil from housing (12). The present invention has solved thisproblem by metering the flow of oil in outlet line (14).

The metering device used in the present embodiment is a needle valve.The needle valve allows the flow rate to be varied depending on theconditions of operation. This metering device is preferred when thepresent invention is initially connected, for reasons as discussedpreviously. When the operating conditions have been balanced, and asuitable flow rate has been found, the needle valve can be replaced witha corresponding fixed orifice valve.

Finally, the oil flow passes through sample valve (23), a section ofbraided flex hose (27b), moisture eye (24), and shut-off valve (21) andreturns to oil pump (32). The reinforced hose is preferable because itresists the extensive mechanical and chemical abuses it is subjected toduring operation.

When refrigeration system (40) is shut down, the negative pressure inoutlet line (14) causes housing (12) to set with an internal negativepressure. This is inherent to only low pressure centrifugal typerefrigeration equipment. Because no seal is perfect, there is naturallysome leakage of atmosphere into the housing. Without proper filtrationof this, contaminant refrigeration system (40) and lubrication system(30) will be subjected to unnecessary corrosive conditions. Others haveused purge pumps to satisfy this problem, but this process releasesenvironmentally harmful refrigerant into the atmosphere. The presentinvention's filtering means and methods allow removal of suchcontaminants without the release of these harmful side affects. While apurge pump will still be utilized because of its advantages to evacuateair from other areas of refrigeration system (40), it is intended thatthe run time due to water in lubrication system (30) can besignificantly reduced.

Another problem which appears to be intrinsic to the centrifugal typeequipment is the use of a water-cooled oil pump. In some instances thewater filled coils which contact the oil within pump (32) will leakwater. Likewise, the condenser and the evaporator section ofrefrigeration system (40) contain water, and sometimes glycol. In theevent of a leak in these systems the water/glycol can migrate into theoil. These leaks cause an inordinate amount of moisture in the oil flowwhich may be undetectable for some time in the systems of the prior artuntil minor damage or even catastrophic failure has occurred. However,the present invention permits detection of these leaks. As the oil isfiltered in filter element (11) the removed water causes slightincreases in the housing pressure. As large amounts of water are removedthe increase in pressure is quite dramatic exhibiting a suboptimalcondition of filter element (11), as it is indicated by gauge (26). Atthis point, when such a pressure increase is noticed, the operator hasseveral options to prevent catastrophic failure within the system.

The foregoing discussion and the claims which follow describe thepreferred embodiments of the present invention. Particularly withrespect to the claims, it should be understood that changes may be madewithout departing from its essence. In this regard, it is intended thatsuch changes would still fall within the scope of the present invention.It simply is not practical to describe and claim all possible revisionsto the present invention which may be accomplished. To the extent suchrevisions utilize the essence of the present invention, each wouldnaturally fall within the breadth of protection encompassed by thispatent. This is particularly true for the present invention since itsbasic concepts and understandings are fundamental in nature and can bebroadly applied.

I claim:
 1. A bypass filter system for use in low pressure centrifugalrefrigeration equipment having a lubricating system and oil supply,comprising:a. a means for transferring a proportion of oil, wherein saidmeans comprises;(1) an inlet line; (2) an inlet shut-off valve attachedto said inlet line; and (3) a positive pressure maintained within saidinlet line; b. a means for filtering said proportion of oil, whereinsaid means comprises:(1) means for removing water, particles of at leastone micron in size, and particles less than one micron is size; and (2)a canister for housing said means for removing water, particles of atleast one micron in size, and particles less than one micron in size,and wherein each of said means for removing is accomplished by at leasta single fibrous filter element; c. a means for changing said fibrousfilter element during continued operation of said refrigeration system;d. a means for returning oil comprising;(1) an outlet line; (2) anoutlet shut-off valve attached to said outlet line; and (3) a negativepressure maintained within said outlet line; e. a means for allowingevacuation of said means for filtering wherein said means for allowingis integral to said canister; and f. a means for isolating said meansfor filtering, wherein said means comprises said inlet shut-off valveand said outlet shut-off valve.
 2. A bypass filter system as describedin claim 1 and further comprising a means for balancing operatingparameters of said filtering system to allow sufficient filtration ofsaid oil without starving said lubricating system of oil.
 3. A bypassfilter system as described in claim 2 and further comprising a means forcontrolling the flow of said oil through said means for filtering, saidmeans for controlling being integral to said means for returning oil. 4.A bypass filter system as described in claim 3 wherein said means forcontrolling flow is variable.
 5. A bypass filter system as described inclaim 3 wherein said means for controlling flow is fixed.
 6. A bypassfilter system as described in claim 5 wherein said means for controllingflow is a fixed orifice.
 7. A bypass filter system as described in claim4 wherein said means for controlling flow is a needle valve.
 8. A bypassfilter system for use in low pressure centrifugal refrigerationequipment having a lubricating system and oil supply, comprising:a. ameans for filtering said oil, wherein said means is maintained at anabsolute positive pressure; b. a means for transferring a proportion ofoil from said supply to said means for filtering, wherein said oil issubjected to a positive pressure within said means for transferring; c.a means for returning said proportion of oil to said supply from saidmeans for filtering, wherein said oil is subjected to a negativepressure within said means for returning; d. a means for balancingoperating parameters of said filter system to allow submicron filtrationof said oil without starving said lubricating system of oil.
 9. A bypassfilter system as described in claim 8 wherein said means for balancingcomprises a means for controlling flow of lubricating oil through saidmeans for filtering, said means for controlling being integral to saidmeans for returning oil.
 10. A bypass filter system as described inclaim 9 wherein said means for controlling flow is variable.
 11. Abypass filter system as described in claim 9 wherein said means forcontrolling flow is fixed.
 12. A bypass filter system as described inclaim 8 wherein said means for filtering said proportion of oilcomprises:(1) a means for removing submicron contaminants; and (2) acanister for housing said means for removing.
 13. A bypass filter systemas described in claim 8 wherein said means for transferring a proportionof oil comprises:(1) an inlet line; and (2) an inlet shut-off valve. 14.A bypass filter system as described in claim 13 wherein said means forreturning oil comprises:(1) an outlet line; and (2) an outlet shut-offvalve.
 15. A bypass filter system as described in claim 8 or 14 andfurther comprising a means for isolating said means for filtering.
 16. Abypass filter system as described in claim 15 wherein said means forisolating comprises said inlet filter shut-off attached to said inletline and said outlet filter shut-off attached to said outlet line.
 17. Abypass filter system as described in claim 16 wherein said means forisolating further comprises a means for allowing evacuation of saidmeans for filtering, wherein said means for allowing is integral to saidcanister.
 18. A bypass filter system as described in claim 17 whereinsaid means for allowing evacuation is a Schrader valve fitting.
 19. Abypass filter system as described in claim 14 and further comprising ameans for detecting moisture in said oil after filtering said oil.
 20. Abypass filter system as described in claim 19 wherein said means fordetecting comprising a moisture eye.
 21. A bypass filter system asdescribed in claim 14 and further comprising a means for verifyingreturn oil flow, and wherein said means for verifying comprises amoisture eye.
 22. A bypass filter system as described in claim 8 whereinsaid means for balancing comprises a means for optimizing retention ofsaid oil in said means for filtering.
 23. A bypass filter system asdescribed in claim 22 wherein said means for optimizing retention isvariable.
 24. A bypass filter system as described in claim 22 whereinsaid means for optimizing retention is fixed.
 25. A bypass filter systemfor use in low pressure centrifugal refrigeration equipment having alubricating system and oil supply, comprising:a. a means fortransferring a proportion of oil from said oil supply, wherein saidmeans for transferring comprises:(1) an inlet line; and (2) a means formaintaining a positive pressure within said inlet line; b. a means forfiltering said oil, wherein said means for filtering comprises:(1) ameans for removing submicron contaminants; and (2) a canister forhousing said means for removing. c. a means for returning oil to saidoil supply, wherein said means for returning comprises:(1) an outletline; and (2) a means for maintaining a negative pressure within saidoutlet line; d. a means for changing said means for removingcontaminants during continued operation of said refrigeration system.26. A bypass filter system as described in claim 25 wherein said meansfor changing comprises a means for isolating said means for filtering,and wherein said means for isolating comprises:a. inlet filter shut-offattached to inlet line; and b. outlet filter shut-off attached to outletline.
 27. A bypass filter system as described in claim 26 wherein saidmeans for isolating further comprises a means for allowing evacuation ofsaid means for filtering, wherein said means for allowing is integral tosaid canister.
 28. A bypass filter system as described in claim 8 or 25and further comprising a means for verifying proper operation of saidmeans for filtering during operation of said refrigeration equipment.29. A bypass filter system as described in claim 28 wherein said meansfor verifying proper operation comprises a means for sampling pre andpost filtered oil.
 30. A bypass filter system as described in claim 12or 25 wherein said means for filtering further comprises a means forremoving water, and wherein said means for removing water is integral tosaid means for removing submicron contaminants, and further wherein saidmeans for removing water and submicron contaminants comprises a fibrousfilter.
 31. A bypass filter system as described in claim 30 wherein saidmeans for filtering further comprises a means for removing glycol,wherein said means for removing glycol comprises said fibrous filter.32. A bypass filter system as described in claim 30 wherein said meansfor removing water comprises a submicron filter element.
 33. A bypassfilter system as described in claim 32 and further comprising a meansfor detecting a clogged filter element.
 34. A bypass filter system asdescribed in claim 33 wherein said means for detecting comprising acompound pressure gauge.
 35. A bypass filter system as described inclaim 8 or 25 and further comprising a means for determining thepresence of a water leak in said refrigeration equipment.
 36. A bypassfilter system as described in claim 35 wherein said means fordetermining comprising a compound pressure gauge.
 37. A bypass filtersystem as described in claim 36 wherein said means for filteringcomprises a canister housing a submicron filter and wherein said housinghas a Schrader fitting, said compound pressure gauge being attached tosaid Schrader fitting, and wherein said system further comprises a meansfor verifying the calibration of said pressure gauge.
 38. A bypassfilter system as described in claim 37 wherein said means for verifyingcomprising a means for detecting moisture in said outlet line.
 39. Abypass filter system as described in claim 8 or 25 wherein saidproportion of oil transferred is in the range of 2-35% of full flow. 40.A bypass filter system as described in claim 8 or 25 wherein saidproportion of oil transferred is in the range of 10-15% of full flow.41. A bypass filter system as described in claim 40 wherein saidproportion of oil drawn off is preferably 10% of full flow.
 42. A bypassfilter system for use in low pressure centrifugal refrigerationequipment having a lubricating system and oil supply, comprising:a. ameans for transferring a proportion of oil comprising;(1) an inletshut-off valve; (2) an inlet line; and (3) a positive pressure withinsaid inlet line; b. a means for filtering said proportion of oilcomprising:(1) a means for removing water, particles of at least onemicron in size, and particles of less than one micron in size; and (2) acanister for housing said means for removing water, particles of atleast one micron in size, and particles of less than one micron in size;c. a means for returning oil comprising;(1) an outlet line; (2) anoutlet shut-off valve; and (3) a negative pressure within said outletline; d. a means for allowing evacuation of said means for filtering,wherein said means for allowing is integral to said canister; and e. ameans for isolating said means for filtering.
 43. A bypass filter systemas described in claim 42 wherein said means for isolating comprises saidinlet shut-off attached to said inlet line and said outlet shut-offattached to said outlet line.
 44. A bypass filter system as described inclaim 43 wherein said means for allowing evacuation is a Schrader valveand wherein said Schrader valve is attached to said canister.
 45. Abypass filter system as described in claim 25 or 42 and furthercomprising a means for balancing operating parameters of said filteringsystem to allow sufficient filtration of said oil without starving saidlubricating system of oil.